A Reduced-Area Scheme for Carry-Select Adders

  • Authors:
  • A. Tyagi

  • Affiliations:
  • -

  • Venue:
  • IEEE Transactions on Computers
  • Year:
  • 1993

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Abstract

The carry-select or conditional-sum adders require carry-chain evaluations for each block for both the values of block-carry-in, 0 and 1. The author introduces a scheme to generate carry bits with block-carry-in 1 from the carries of a block with block-carry-in 0. This scheme is then applied to carry-select and parallel-prefix adders to derive a more area-efficient implementation for both the cases. The proposed carry-select scheme is assessed relative to carry-ripple, classical carry-select, and carry-skip adders. The analytic evaluation is done with respect to the gate-count model for area and gate-delay units for time.